Effect of Soil Type on the Establishment of Grape Phylloxera Colonies in the Pacific Northwest

Abstract

Soils from the Pacific Northwest were investigated to determine if soil type affects the establishment of new phylloxera populations. Soils included those of the Abegg, Helvetia, and Jory series in Oregon, the Burke series in Washington, and two artificial soils, a soilless mix and a Jory/sand mix. Vitis vinifera cv. Pinot noir vines in each soil were infested with phylloxera eggs originating from the Willamette Valley in western Oregon and the Yakima Valley in eastern Washington. After three months, phylloxera numbers were collected through investigation of soil core samples. Soils from all six soil types supported phylloxera establishment, regardless of population origin. Overall, soil from the Burke series had the lowest percentage of establishment and significantly lower population means. All Oregon soil types and the artificial mixes consistently supported higher population numbers of phylloxera. Based on establishment and proliferation of population numbers in the Burke series soil, we conclude that some soils may provide an environment that suppresses the growth of phylloxera populations. However, none of the soils tested in this study prevented grape phylloxera establishment.